Ocean waves generate both horizontal and vertically rotating oscillating movements, as described in patent application US2007/0158950 and patent application U.S. Pat. No. 7,385,301. The oscillating movements can contain tens and sometimes hundreds of kW per running meter wave and has therefore been subjected to several attempts of creating systems that are able to convert this enormous amount of energy into useful and competitive energy transformers converting the energy into for example electric power. In order to achieve these goals it is not enough to use different types of block diagrams to disclose how a certain energy transformer converts wave movement into for example rotational movements, not without at the same time describe why this certain construction have the requirements for a long lifetime with low supervision and maintenance cost.
The present invention is aiming to create a compact and cost efficient energy transformer unit which functionally and geometrically has been optimized to, by using well-known methods and experiences, be able to calculate life and maintenance costs with regard to material, fluids, gases, and mechanical, electric and electronic components.
The invention has been inspired by the applicants discoveries on the actual pump and automatic control functions of the heart, described in the paper “Cardiac Pumping and Regulating Functions of Intraventricular Septum” (Lundbäck 1986). In the paper the discovery of a new pump principle was disclosed, now named Dynamic Adaptive Piston pumps (DAP) also disclosed as DeltaV-pumps (ΔV-pumps), see U.S. Pat. No. 4,648,877. These pumps take advantage of the best characteristics of the two earlier known pump principles; the dynamic pump principle (for example centrifugal pumps) and the displacement pump principle (for example piston pumps). The ΔV-pump can during lower flows and frequencies be regarded as a displacement pump where the piston is so designed that it with a one-way directed force, besides a pump work also produces a reciprocating volume, ΔV-volume, which can store and convert energy in order to generate a hydraulic return of the piston, named ΔV-function. The new pump function, which is the same as the real pump function of the heart, has mathematically been described in U.S. Pat. No. 7,239,987.
The nature has both constructed and energized the heart like a ΔV-pump, using the characteristics and functions of the heart muscular cells. These cells perform their work by one-way longitudinal reductions and contractions and need stored energy, ΔV-functions, for their return movement. The one-way power generation of the muscular cells and the hydraulic return of the piston like cardial valve planes of the heart can be compared with the heaving power generation of the waves and has inspired to the present invention; a compact energy transformer.
In order to convert the energy of the ocean waves into mechanical work and/or electric current, energy generating arrangements are required which are able to convey the vertical and/or horizontal forces to the wave movements created by the movements of the water molecules. At larger depth the waves are circular water molecular movements which decreases in intensity the further away from the surface the measurements or energy absorption are performed. At more shallow depth the waves are elliptic water molecular movements. The vertical forces of the waves are in relation to their horizontal forces at lager depth the same, i.e. 50/50%. At smaller depths the vertical forces are more and more added to the horizontal forces, which together with for example the friction to the bottom finally create a break of the wave.
In order to further explain where the present invention can be used as simple and cost effective energy converting units, some examples are below given where historically well-known energy generating arrangements are connected to more or less complex energy transformers of a later date.
In U.S. Pat. No. 1,791,239 (1931, original 1919 OWC, Oscillating Water Column) Braselton describes a way of translating wave energy into electric power by letting the movements of the waves to work as a large piston in a “cylinder”-wave catcher. The movement of the waves translates a large flexible and compressible amount of air towards a converging pipe. In this pipe an air turbine is mounted which transforms the flow of air into electric power. The large and often land based OWC-constructions have a very low efficiency. This is, among other things, due to the difficulty for the air turbines to handle large variations in pressure and flow, which is the result of the reciprocating movement of the air. The Norwegian University of Science and Technology (NTNU) located in Trondheim Norway, did during the 70's and 80's, under the guidance of Budal, perform an extensive study on the OWC-technique by using Point Absorbers (buoys on the ocean surface). In 2003 an abstract was published with conclusions from these studies. In the abstract they revealed that in order to in a cost effective way translate wave energy into electric power, the usage of elastic air as a force translator should be converted into modern hydraulics with latching-controlled buoy movements. Further it was revealed that “small is beautiful”, i.e. that the buoy size should not be larger that 5-10% of the wave length, and that the latch technique also was able to protect the whole system during bad weather. Experiments with the OCW-technique are still ongoing, for example by improving the efficiency of the turbines.
U.S. Pat. No. 4,355,511 (1982) describes embodiments where, for example, the latch technique is used.
U.S. Pat. No. 4,172,689 (1979) describes a way where a floating buoy or a craft is arranged so that it collects the waves on one side and converts these towards a water turbine on the opposite side of the craft. This energy absorbing method, plus other methods that utilizes the differences between wave crests and wave troughs on the ocean surface, for example the Pelamis “sea snake”, require large constructions to function.
U.S. Pat. No. 4,001,597 (1977) describes how a bottom based energy carrying unit, “wave tilter”, on shallow water can be brought to tilt backwards and forwards depending on the horizontal forces of the motion of the waves. The motions of the wave tilters affect water cylinders providing land based turbines with water flow. One example where this technique is used is Aquamarine's sea-wave power technique Oyster Wave Energy Converter, where the “wave tilter” operates water cylinders which under high pressure provide land based pelton-type turbines with water flow. Another example is U.S. Pat. No. 7,131,269 (2006) where the wave tilter via a piston compresses air, taken from above the water, and via an air-lift-pump at the bottom generates a water flow that operates a turbine. Another example is US 2006/0150626 (2006) A1 where a revolving displacement pump with various one way valves are connected to a wave tilter to provide an adjacent hydraulic system with pressurized fluid.
U.S. Pat. No. 3,989,951 (1976) describes how a bottom based energy carrying unit with a flexible rubber membrane catches statistical pressure variations generated by crests of waves and trough of waves at the ocean surface. These pressure variations transfer a gas over a gas turbine producing electric current. This converter should have efficiencies that are comparable with the classical OWC-converter.
U.S. Pat. No. 6,229,225 filed May 1998 and U.S. Pat. No. 6,392,314 filed December 1998 display an embodiment of U.S. Pat. No. 3,989,951 (1976) where a flexible buoy located under the water surface is affected by the wave motions' statistical pressure variations such that compression and decompression of a buoy give displacement changes. This result in variations in pulling forces that can be used to produce mechanical work. The size of the buoys and the migration of the gases through the flexible buoy material may cause long-term problems.
U.S. Pat. No. 4,081,962 (1978) display how a reactive mass under the water surface can be used to create forces opposite to the water motions on the water surface and how these opposite forces can be used to extract energy. Several modifications of this basic concept have been made throughout the years. Wavebob is an example where this technique is being used.
In U.S. Pat. No. 1,318,469 (1919), Wilkinson introduces a simple device where a rope connected to a buoy is used to transform the buoy's motions to mechanical work. Others have with the same basic idea presented solutions which with help from endless wires, belts, chains and gear racks converts the buoy motions to rotating motions of an axis, which can be used for example for the production of electric power. These converting manners give, through its direct connection to the buoy, an efficiency that mostly is determined from the generators efficiency at different number of revolutions. With assistance from the latch-technique that was showed by Budal, however often forgotten or impossible to implement, you can by affecting the buoy's motions in waves optimize the energy absorption from the waves and the efficiency of the converter system.
The life of the seemingly very simple and easily comprehensible constructions is in terms of rope- and wire constructions very short, even during the most optimal conditions. The life for constructions with belts, chains and gear racks can be made considerably longer if they operate under optimal conditions. Another troublesome factor regarding these purely mechanical constructions is to find lasting solutions to protect systems when they reach their closing position. Shock absorbers in the form of steel springs and rubber can be heavy, volume-consuming and create back springing forces that are not always positive.
In U.S. Pat. No. 628,657 (1899) Max Gehre introduces devices which by using buoys and linear generators can generate current from wave movements. This concept has been an object for a number of variants over the years. The problems with these generators are, despite today's magnetic materials, that they in relation to fast rotating generators are bulky, heavy and expensive. These seemingly simple constructions must however be supplemented with an additional latch-technique, shock absorbers and systems to prevent water leakage through the linear passages in connection to the generator room. Furthermore, these systems can't as individual sources of power, be provided with simple devices that levels out energy production.
The most general way to transfer the wave absorbers backward and forward motions to rotary motion is made by means of hydraulics where water or oil operates a turbine or hydraulic engine connected to a generator. The “wave tilter” is ideal for these kind of technique because it is affected by double-acting forces that can be recovered by double-acting pistons or rotating cylinders. On the other hand, point absorbers (buoys) do need some form of energy to perform their accumulated return movements.
The patent application US 2005/0167988 presents an example on how you, by using conventional hydraulic connections, can transform backward and forward motions of a “point absorber” into electric current. This patent application can also serve as background to clarify the differences of the present innovation. The floating buoy in patent application US 2005/0167988 is flexibly connected to a hollow piston rod which hydraulic cylinder via an extension pipe is flexible connected to a hollow piston shaft whose hydraulic cylinder via an elongating pipe is elastically connected to a buoy sinker at the bottom of the sea. Via a piston shaft and a piston the buoy generates a piston displacement which is, by the hollow piston rod, under a high pressure accumulated in a high pressure chamber located in the buoy. This high pressure chamber is, via a controlled variable hydraulic engine and a cooling system, in contact with another pressure chamber with low pressure. The hydraulic engine transforms via a generator the pressure differences within the flow between the both chambers to electric current. The remaining pressure in the low pressure chamber is used to bring back the piston and also the connected buoy to a new starting position in the following trough of the sea. A control system with ventilators and a small pump connected to a reservoir add or remove oil from the system in order to get the pressures in the accumulator tanks to be the right at different times, wave heights, weather situations, etc., so that a continuous flow over the hydraulic motor can be performed during the piston's and the buoy's return movements.
This system is one-way acting i.e. the system utilizes and stores the wave energy during the rising phase of the wave motions to distribute this energy through an arrangement of large accumulator tanks during the whole wave period. The large pressure differences can create problem of gas migration between the accumulator tanks, thus frequent controls must be performed.